The present invention relates to a chain especially adapted to connect the pulleys of a pulley transmission, particularly a variable pulley transmission. The chain includes two half-chains with each carrying a full-width strut. The half-chains are placed in a side-by-side relationship and offset from each other by one-haft the pitch distance so that half-chains are out of phase. The struts are interleaved with file free ends supported by the links of the opposing half-chain. It is expected that the offset of the half-chains will reduce the noise generation of the chain.
Variable pulley transmissions for transferring torque from an input or drive shaft to an output or driven shaft have been used for some time. In these transmissions, a first pulley constructed of a pair of sheaves or flanges is mounted on the input shaft such that at least one of its sheaves is axially movable with respect to its other sheave. A second, similarly constructed and adjustable pulley is mounted on the output shaft. A chain connects and transfers torque between the two pulleys when the input shaft is driven. As the effective diameter of one pulley is changed, the effective diameter of the other pulley is changed in the other direction and, the drive ratio between the input and output shafts is adjusted in a smooth, continuous manner.
In one type of variable pulley transmission chain, the chain links are provided in sets that are interleaved together. The links have aligned apertures for receiving pivot members. The pivot members can provide the means for the transfer of power between the chain and the sheaves of the pulley by allowing the sheaves to directly contact the ends of the pivot members in a driving engagement.
Load blocks or load carrying members that are positioned on the chain between the spaced pivot members can also provide the means for transfer of power between the pulleys. The load blocks can extend around the links of the chain and have one or more windows for receiving the chain links therein. The load blocks have tapered outer or end surfaces which engage the sheave faces of the pulleys to provide the driving engagement between the pulleys and the chain. Examples of such power transmission chains suitable for use in a continuously variable transmission are shown in U.S. Pat. Nos. 4,911,682 and 4,507,106.
Alternatively, the load blocks can be in the form of struts that are carried in a passageway below the links. An example of this type of chain is shown in U.S. Pat. Nos. 5,007,883 and 5,026,332. In this type of chain at least some links in some sets have toes or protrusions defining a passageway that receives power transmitting struts
When the above transmission chains are used, noise is generated as the load blocks or struts contact the sides of the pulleys. Increasingly, however, consumers desire a more quiet environment. As a result, efforts have been directed to decrease the noise associated with the operation of the chain.
One solution has included using links of more than one pitch length, changing the length of the struts, and changing the length of the chain receiving windows. By altering these pulley engaging characteristics of the chain, the noise pattern associated with the operation of the chain is modified and becomes more acceptable.
Another solution has been to use two chains positioned in a side-by-side relationship and out of phase with respect to each other by one-half the pitch distance. An example of this type of chain is shown in U.S. Pat. No. 5,215,505 which shows load blocks in the form of an I-shaped friction plate. The friction plate has a left and a right recess each of which receives a chain. Each chain comprises the same number of interleaved links of uniform thickness, with the chains positioned out of phase with each other by one-half the pitch distance, i.e., the center of the pivot pins of one chain project to about halfway between the centers of two adjacent pivot pins of the other chain. One friction plate is engaged in top and bottom notches in the links in one chain and the adjacent friction plate is engaged in top and bottom notches in the links in the other chain.
The chain of the present invention, on the other hand, provides a strut type of power transmitting load block with two chains positioned in a side-by-side relationship and offset from each other. Each strut has a lateral or transverse width substantially equal to the overall transverse width of the two chains. A portion of each strut is securely carded in a passageway defined by toes provided on the links of one chain with the other portion of the strut, i.e., the free end of the strut, supported by the links of the other chain. The struts therefore enjoy a measure of lateral freedom of movement that enhances the overall durability of the struts. As a result, the chain is expected to be more durable. In addition, because the full-width chain includes two half-chains offset from each other it is expected to result in a decrease in the noise associated with the operation of the chain.